PoC service defines various requirements considering different PoC user groups and the nature of participation of the PoC users in the PoC groups. One unique feature of the PoC service is to prioritize media control requests. When a PoC user requests for media according to his priority, a controlling PoC server entity identifies the media request along with the priority of the user.
Currently, three priority levels are defined in the PoC service, namely, normal user, high-priority user, and pre-emptive user. A normal PoC server grants a media floor to media requests as the requests come in order. When more than one normal PoC user makes a media request, their requests will be queued in the order they come. A high-priority PoC user has a higher priority, compared to normal PoC users, when his media request is queued for the media floor. Even though the high-priority PoC user requests the floor later than a normal PoC user, his request is queued with priority over the request from the normal user to get the floor earlier. If queuing of media requests is not supported, the floor is granted to users in the order that their requests come irrespective of their priority levels. A user can't take precedence over other users who have requested with the same priority. In such a case, their media requests will be queued in the order that they come in.
A PoC user requesting with pre-emptive priority will normally get the floor immediately irrespective of other normal or high-priority PoC users are sending media when he requests the floor. Hence, at the moment the pre-emptive PoC user requests the floor, the media burst transmission from the normal or high-priority PoC user is interrupted.
FIG. 1 illustrates a media controlling procedure when a pre-emptive PoC user requests for media.
Referring to FIG. 1, PoC Client B sends media in a PoC session in steps 100 to 103. PoC Client A being a pre-emptive PoC user needs to immediately send media during receiving the media from PoC Client B and thus sends a Media Burst Request message to a controlling PoC server in steps 104 and 105.
Controlling PoC Server X (controlling) determines whether PoC Client B has a pre-emptive right. If PoC Client B is not a pre-emptive user, Controlling PoC Server X revokes the permission to send the media from PoC Client B by sending a Stop Talk Burst message, subject to the server policy in steps 106 and 107.
PoC Client B sends to PoC Server X the last buffered media packet in steps 108 and 109 and sends a Media Burst Complete message to Controlling PoC Server X in steps 112 and 113.
In steps 110 and 111, Controlling PoC Server X forwards the last media packet received from PoC Client B to PoC Client A. It also sends a Media Burst Confirm message to PoC Client A in steps 114 and 115.
Upon receipt of the Media Burst Confirm message, PoC Client A notifies PoC User A that media transmission is available. PoC Client A then begins to send media to Controlling PoC Server in steps 116 and 117. Controlling PoC Server forwards the media to the other PoC clients participating in the PoC session except for the transmitting PoC user in steps 120 and 121. Before the media forwarding, Controlling PoC Server notifies the other PoC clients that the pre-emptive PoC user will send media by sending a Receiving Media Burst message.